How to bend/shape Plywood?

by Greg
(New Zealand)

Hi, I'm a first timer and want to build a 10 to 12 ft dingy using the stitch and glue method.

I've done a lot of reading on the website but can't find any advice on how to bend/shape some of my plywood pieces before I stitch them.

Any advice please?

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How to bend/shape Plywood?

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Bending Plywood
by: Mike

Hi Greg,

Most designs for a dinghy of that size will have relatively gentle curves.

And the plywood needed to build her will be relatively thin and flexible.

I think you will find that the plywood once cut to size will easily flex enough to bend ‘cold’ around your shape.

However, that said if you do find you are having difficulties with for instance the nib ends there are a number of strategies which can help.

Steam bending is not something I would recommend for plywood.

An alternative is to wrap the area which needs most bending in towels then pour on hot water.

Or simply soak the ply overnight and encourage the bending by propping it on some batons then placing a weight on top.

But as you are going to be using Epoxy you will have to make absolutely certain that the plywood is completely dry again before gluing it up, epoxy and moisture do not mix.

In some cases it is just that you cannot get enough leverage on say a nib end.

In which case if you cut the plank over length it will give you the leverage to get the end in position, clamp and fasten it, then trim it off afterwards.

If it needs to be cut to size before gluing you could clamp a long baton onto the ply and use that to give you the extra leverage.

For a very tight radius it is probably best to laminate it up from several layers of thinner (more flexible) ply.

The number of ‘plys’ will also affect the plywood’s flexibility.

The more piles there are the more the crosswise strength will increase.

With three ply the strength is greatest along the surface grain axis, as there are two layers with grain in that direction but only the one, the core, with its grain running at right angles.

The five ply gives you two more veneers running at right angles so the cross strength/stiffness increases.

But much depends on the design of the hull, if you can give us some more details we might be able to offer more specific advice.

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